C/2021 G2 (ATLAS)
| Parameter |
Value |
| Designation |
C/2021 G2 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2024-09-09T05:14:56.440320Z |
| Orbit solution date (soln_date, UTC) |
2026-01-07T15:42:41Z |
| Obs used |
3649 |
| NEO |
- |
| M1 |
8.000 |
| K1 |
5.250 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2024-08-14.0000000 |
| e |
1.00020732 |
| q (au) |
4.982424 |
| a (au) |
-24032.772651 |
| i (deg) |
48.473423 |
| Ω (om, deg) |
221.094941 |
| ω (w, deg) |
343.279145 |
| M (ma, deg) |
-0.000007 |
Magnitude
Scatter + Global Linear
$$
M_a = (4.916 + 3.073\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
4.916 |
| n |
3.073 |
| gf |
0.857 |
| gb |
-0.949 |
| k |
1.000 |
| δ90 |
6.616 |
| Parameter |
Symbol |
Range |
Description |
| Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
| Photometric slope parameter |
n |
2 to 6 |
Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
| Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
| Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
17:12:05.96 |
+02:30:49.2 |
HIP 84163 |
23.72 |
| 2026-02-03 12:00 |
17:12:23.07 |
+02:33:26.6 |
HIP 84163 |
26.00 |
| 2026-02-04 00:00 |
17:12:40.08 |
+02:36:04.8 |
HIP 84163 |
29.00 |
| 2026-02-04 12:00 |
17:12:56.98 |
+02:38:43.9 |
HIP 84163 |
32.50 |
| 2026-02-05 00:00 |
17:13:13.78 |
+02:41:23.9 |
HIP 84163 |
36.35 |
| 2026-02-05 12:00 |
17:13:30.47 |
+02:44:04.7 |
HIP 84163 |
40.44 |
| 2026-02-06 00:00 |
17:13:47.06 |
+02:46:46.5 |
HIP 84384 |
43.37 |
| 2026-02-06 12:00 |
17:14:03.53 |
+02:49:29.1 |
HIP 84384 |
39.17 |
| 2026-02-07 00:00 |
17:14:19.90 |
+02:52:12.6 |
HIP 84384 |
35.14 |
| 2026-02-07 12:00 |
17:14:36.16 |
+02:54:57.0 |
HIP 84384 |
31.37 |
| 2026-02-08 00:00 |
17:14:52.30 |
+02:57:42.2 |
HIP 84384 |
27.94 |
| 2026-02-08 12:00 |
17:15:08.34 |
+03:00:28.3 |
HIP 84527 |
24.24 |
| 2026-02-09 00:00 |
17:15:24.26 |
+03:03:15.2 |
HIP 84527 |
20.64 |
| 2026-02-09 12:00 |
17:15:40.07 |
+03:06:03.1 |
HIP 84527 |
17.68 |
| 2026-02-10 00:00 |
17:15:55.77 |
+03:08:51.7 |
HIP 84527 |
15.72 |
| 2026-02-10 12:00 |
17:16:11.35 |
+03:11:41.3 |
HIP 84517 |
14.27 |
| 2026-02-11 00:00 |
17:16:26.82 |
+03:14:31.6 |
HIP 84517 |
10.11 |
| 2026-02-11 12:00 |
17:16:42.17 |
+03:17:22.8 |
HIP 84517 |
6.82 |
| 2026-02-12 00:00 |
17:16:57.41 |
+03:20:14.9 |
HIP 84517 |
6.01 |
| 2026-02-12 12:00 |
17:17:12.53 |
+03:23:07.8 |
HIP 84517 |
8.40 |
| 2026-02-13 00:00 |
17:17:27.53 |
+03:26:01.5 |
HIP 84517 |
12.22 |
| 2026-02-13 12:00 |
17:17:42.41 |
+03:28:56.0 |
HIP 84517 |
16.50 |
| 2026-02-14 00:00 |
17:17:57.17 |
+03:31:51.4 |
HIP 84517 |
20.94 |
| 2026-02-14 12:00 |
17:18:11.81 |
+03:34:47.6 |
HIP 84517 |
25.46 |
| 2026-02-15 00:00 |
17:18:26.33 |
+03:37:44.6 |
HIP 84632 |
29.41 |
| 2026-02-15 12:00 |
17:18:40.73 |
+03:40:42.4 |
HIP 84594 |
29.13 |
| 2026-02-16 00:00 |
17:18:55.01 |
+03:43:41.0 |
HIP 84594 |
29.07 |
| 2026-02-16 12:00 |
17:19:09.16 |
+03:46:40.5 |
HIP 84594 |
29.70 |
| 2026-02-17 00:00 |
17:19:23.19 |
+03:49:40.7 |
HIP 84828 |
29.02 |
| 2026-02-17 12:00 |
17:19:37.10 |
+03:52:41.7 |
HIP 84828 |
24.85 |
| 2026-02-18 00:00 |
17:19:50.88 |
+03:55:43.5 |
HIP 84828 |
20.85 |
| 2026-02-18 12:00 |
17:20:04.53 |
+03:58:46.0 |
HIP 84828 |
17.13 |
| 2026-02-19 00:00 |
17:20:18.06 |
+04:01:49.3 |
HIP 84828 |
13.92 |
| 2026-02-19 12:00 |
17:20:31.46 |
+04:04:53.4 |
HIP 84828 |
11.61 |
| 2026-02-20 00:00 |
17:20:44.73 |
+04:07:58.3 |
HIP 84828 |
10.79 |
| 2026-02-20 12:00 |
17:20:57.87 |
+04:11:03.9 |
HIP 84828 |
11.75 |
| 2026-02-21 00:00 |
17:21:10.88 |
+04:14:10.2 |
HIP 84828 |
14.12 |
| 2026-02-21 12:00 |
17:21:23.77 |
+04:17:17.3 |
HIP 84828 |
17.32 |
| 2026-02-22 00:00 |
17:21:36.52 |
+04:20:25.1 |
HIP 84899 |
18.74 |
| 2026-02-22 12:00 |
17:21:49.14 |
+04:23:33.7 |
HIP 84899 |
17.87 |
| 2026-02-23 00:00 |
17:22:01.63 |
+04:26:43.0 |
HIP 84899 |
18.04 |
| 2026-02-23 12:00 |
17:22:13.99 |
+04:29:52.9 |
HIP 84899 |
19.23 |
| 2026-02-24 00:00 |
17:22:26.22 |
+04:33:03.6 |
HIP 84899 |
21.25 |